1. Field of the Invention
The present invention relates to an optical coordinate input apparatus. In particular, the invention relates to an optical coordinate input apparatus in which a plurality of light emitting devices are arranged on one side of two sides opposite in horizontal direction (opposite in X direction) of a rectangular operational area in a display device while a plurality of light receiving devices are arranged on the other side thereof so that each of the plurality of light receiving devices faces each of the plurality of light emitting devices, and at the same time, a plurality of light emitting devices are arranged on one side of two sides opposite in vertical direction (opposite in Y direction) of the rectangular operational area in the display device while a plurality of light receiving devices are arranged on the other side thereof so that each of the plurality of light receiving devices faces each of the plurality of light emitting devices, wherein beams emitted from the plurality of light emitting devices are arranged in X-Y matrix inside the operational area, and wherein, when a light shielding signal is detected through a light receiving devices in X direction and also through a light receiving devices in Y direction, the optical coordinate input apparatus determines that the display device is touched at an intersection of a line from the light receiving devices in X direction and a line from the light receiving devices in Y direction, and inputs the coordinates of the intersection.
2. Description of Related Art
There have been conventionally proposed various types of coordinate input devices which are disposed on display devices such as a liquid crystal display and detect positions touched on the display devices with fingers and the like. The types of the coordinate input devices include a resistive-film type, a surface acoustic wave type, an optical (infrared light) type, an electromagnetic induction type, an electrostatic capacitance type and the like. Among them, an optical-type coordinate input device has been widely employed in, for instance, an automatic teller machine in a bank, a ticket vending machine in a railroad station, etc. since the optical-type coordinate input device has high light transmission property and also has excellent transparency and reliability.
The optical coordinate input apparatus of this kind as described in Japanese Laid-open Patent Application No. 2004-295644 is generally configured to dispose plural sets of light emitting diodes on one horizontal side of a rectangular operational area defined in a display device and on one vertical side thereof respectively, and also to dispose a plurality of phototransistors on the other horizontal side of the operational area and on the other vertical side thereof so that the plurality of phototransistors are spaced from and facing the respective light emitting diodes.
Here, in the conventional optical coordinate input apparatus, the plurality of light emitting diodes disposed on one horizontal side of the rectangular operational area are illuminated, and also the plurality of light emitting diodes disposed on one vertical side thereof are illuminated. As a result, beams emitted from the pluralities of light emitting diodes form an X-Y matrix in the operational area. When a light shielding signal is detected simultaneously at each of a phototransistor disposed in X direction and a phototransistor disposed in Y direction, it is determined that the display device has been touched on an intersection of a line from the phototransistor disposed in X direction and a line from the phototransistor disposed in Y direction.
However, such a conventional optical coordinate input apparatus is originally designed to detect only one touch position in one input operation performed by a finger, a pen, etc. in the rectangular operational area. Accordingly, there is not disclosed or suggested any control with respect to a case where the display device is touched on more than one touch position simultaneously in the rectangular operational area.
Here, in an optical coordinate input apparatus, even when an ordinary operator intends to touch the two points simultaneously, it is practically impossible to touch two points exactly simultaneously. There will occur at least more than 1 ms of time lag between touch timings on the two points, based on ergonomics.
Under these circumstances, in a case where a scan time is more than 1 ms for detecting light shielding signals by sequentially scanning light emitting elements or light receiving elements in the optical coordinate input apparatus, more than one touch position may be detected within one scan time.
Details of the above case will be given referring to FIG. 5 and FIG. 6. FIG. 5 and FIG. 6 are explanatory views each illustrating a frame format when two touch positions are detected within one scan time.
In FIG. 5, an optical coordinate input apparatus 100 has a light emitting unit 101 and a light receiving unit 102 both of which are L-shaped. In an area surrounded by the light emitting unit 101 and the light receiving unit 102, a rectangular operational area 103 is formed. Nine light emitting elements 104 are aligned in vertical direction in a vertical portion (Y-side portion) of the light emitting unit 101, and another nine light emitting elements 104 are aligned in horizontal direction at a horizontal portion (X-side portion) of the light emitting unit 101.
Also, nine light receiving elements 105 are aligned in vertical direction in a vertical portion (Y-side portion) of the light receiving unit 102, and another nine light receiving elements 105 are aligned in horizontal direction at a horizontal portion (X-side portion) of the light receiving unit 102.
In the optical coordinate input apparatus 100, each of the light emitting elements 104 aligned at the vertical portion of the light emitting unit 101 and each of the light receiving elements 105 aligned at the vertical portion of the light receiving unit 102 are placed to face each other. Beams emitted from the light emitting elements 104 are respectively received through the light receiving elements 105. Also, each of the light emitting elements 104 aligned at the horizontal portion of the light emitting unit 101 and each of the light receiving elements 105 aligned at the horizontal portion of the light receiving unit 102 are placed to face each other. Beams emitted from the light emitting elements 104 are respectively received through the light receiving elements 105. As a result, in the operational area 103, beams emitted from the respective light emitting elements 104 form an X-Y matrix, as illustrated in FIG. 5.
Here is a case as illustrated in FIG. 5 where an operator has touched a point A and a point B in this order with two fingers. In this case, the point A is located at an intersection of a beam emitted from the seventh light emitting element 104 downward from the top at the vertical portion of the light emitting unit 101 and a beam emitted from the third light emitting element 104 rightward from the left at the horizontal portion thereof. As each of the above beams is shielded at the intersection, a light shielding signal S is detected at the seventh light receiving element 105 downward from the top at the vertical portion of the light receiving unit 102, and at the same time, a light shielding signal S is detected at the third light receiving element 105 rightward from the left at the horizontal portion thereof. In the similar manner, the point B is located at an intersection of a beam emitted from the third light emitting element 104 downward from the top at the vertical portion of the light emitting unit 101 and a beam emitted from the seventh light emitting element 104 rightward from the left at the horizontal portion thereof. As each of the above beams is shielded at the intersection, a light shielding signal S is detected at the third light receiving element 105 downward from the top at the vertical portion of the light receiving unit 102, and at the same time, a light shielding signal S is detected at the seventh light receiving element 105 rightward from the left at the horizontal portion thereof.
As has been described above, in the optical coordinate input apparatus 100, the time required for one scan is more than 1 ms. As a result, even though the operator has touched the point A and the point B in this order, it is impossible to recognize the order of the touches based on the timings of scanning, when the point A and the point B are detected in one scan time.
Here is a case, as illustrated in FIG. 6, where a quadrangle is assumed to have the point A and the point B as two opposite vertices and a point C and a point D are set as the other two opposite vertices. There, the point C and the point D are touched in this order within one scan time. The point C is located at an intersection of a beam emitted from the seventh light emitting element 104 downward from the top at the vertical portion of the light emitting unit 101 and a beam emitted from the seventh light emitting element 104 rightward from the left at the horizontal portion thereof. As each of the above beams is shielded at the intersection, a light shielding signal S is detected at the seventh light receiving element 105 downward from the top at the vertical portion of the light receiving unit 102, and at the same time, a light shielding signal S is detected at the seventh light receiving element 105 rightward from the left at the horizontal portion thereof. In the similar manner, the point D is located at an intersection of a beam emitted from the third light emitting element 104 downward from the top at the vertical portion of the light emitting unit 101 and a beam emitted from the third light emitting element 104 rightward from the left at the horizontal portion thereof. As each of the above beams is shielded at the intersection, a light shielding signal S is detected at the third light receiving element 105 downward from the top at the vertical portion of the light receiving unit 102, and at the same time, a light shielding signal S is detected at the third light receiving element 105 rightward from the left at the horizontal portion thereof.
Here, the result of the light shielding signals S obtained in the case of FIG. 5 and the result of the light shielding signals S obtained in the case of FIG. 6 are completely identical. Considering these results, even when the point A and the point B are touched as illustrated in FIG. 5, the point C and the point D may be recognized to be touched as illustrated in FIG. 6, and vice versa.